Originally Posted by rover67
Yeah Dave, glad you pointed that out, I have noticed a big difference in quality on some of these relays... Good Idea to order them from a place that you can get good ones. I'll have to do that for my spares.
It's also worth pointing out that most times the rating stamped or implicit in the part number is for purely resistive loads. So a 30A relay is designed to switch 30A into a light bulb, for example. But this relay would not switch 30A into a motor for very long, typically the derating is ~1/3rd. IOW, a 30A relay good for 250K cycles is really only guaranteed for 20A reactive and likely for a reduced number of cycles at that. If the ARB compressor draws say 20A and being that we drive our trucks in hot and cold temps, mud and crud, it's best to be very conservative and use a 40A or 50A relay, which will probably last for 100K cycles. Most likely the plastic will get brittle and break before the contacts weld.